Update On The Race To Build A Quiet Supersonic Jet

RevJim writes: "Popular Science is running this story on the race to build a supersonic jet that reduces or eliminates the 'sonic boom' associated with exceeding the sound barrier. From the article: 'Gulfstream plans to start manufacturing the plane -- its so-called quiet supersonic jet, or QSJ -- by 2006.' Supersonic for the masses closer than we think? Probably not, at $80 million for a 14-passenger jet, but still cool."

Just a thought that's been nagging me for a while

[The_Guv'na]

I know what the little dimples on golf balls are for. They make it fly further by reducing turbulance behind the ball.

Would the same thing help jets fly faster/quieter? The way I see it is that if the jet moves through the air easier, less kinetic energy is wasted making a sonic boom.

And now, for your viewing pleasure... some [igen.ubc.ca] really [nasa.gov] cool [aeropages.co.za] images! [nasa.gov] (that last one's a big + slow, but worth it)

Ali

Golf ball dimples

[teridon]

I know what the little dimples on golf balls are for. They make it fly further by reducing turbulance behind the ball.

No, actually, the dimples increase the turbulence. This is good thing because it means turbulent airflow remains attached to the surface longer. With a smooth ball, the flow lends to remain laminar (smooth), but it detaches from the surface of ball. A detached flow creates more drag than turbulent flow would.

Some airplane wings have vortex generators on the upper surface to cause turbulent flow, reducing the likelihood of a flow detachment.

A more techinal explanation is available here [virginia.edu].

Re:Just a thought that's been nagging me for a whi

[Lars T.]

There have been experiments with planes whose hull (via a film) have a texture like shark's skin (wich is full of tiny teeth). It resulted in a couple of percent less fuel usage.

Destructive interference?

[dacarr]

I remember reading about this phenomenon, where inverting a sound wave would cancel the sound out at a given frequency. Would this work for the likes of sonic booms?

Re:Destructive interference?

[norhythmsoldier]

So, if two supersonic jets collide head on and the shock waves cancel each other out, does it make a sound?

Re:Destructive interference?

[dacarr]

Only if one of them is inverted relative at the time of the collision.

Oh, Popular Science

[Animats]

Wow, we could have supersonic bombers that could get to their targets faster than the B-52.

Like the B-58 Hustler. [b-58hustler.com] Worked fine. Intended for delivery of nuclear weapons to USSR. Obsoleted by ICBMs. High operating costs, small bomb load.

Who said supersonic jets are expensive?

[andika]

... the last five were sold to British Airways and Air France for one French franc apiece [popsci.com].

I'll take two of that please.